Distributor for viscous fluid spinning melts or solutions

ABSTRACT

A distributor for viscous fluid spinning melts or solutions in apparatus for extruding or spinning high molecular weight polymers, especially synthetic fiber-or film-forming polymers, the distributor essentially including at least one ring conduit into which there are connected through lateral ports a plurality of sources and sinks for the fluid, there being at least one source with two or more sinks or at least one sink with two or more sources, each source or sink being connected to the ring conduit in an arrangement such that a substantial pressure difference exists as between a source and two adjacent sinks or between a sink and two adjacent sources, and valve means preferably in the form of poppet valves adapted to open and close individual ports while keeping the cross-section of the ring conduit substantially open, thereby maintaining a minimum flow or circulation of the viscous fluid material throughout the distributor.

United States Patent [1 1 Itter 1 Apr. 3, 1973 [54] DISTRIBUTOR FOR VISCOUS FLUID SPINNING MELTS OR SOLUTIONS [75] Inventor: Friedhelm Itter, Remscheid, Germany [73] Assignee: Banner Barmag Maschinenfabrik Aktiengesellschalt, Wuppertal, Germany [22] Filed: May 5, 1971 [21] Appl. No.: 140,423

[52] US. Cl ..l37/597, 239/562 [51] Int.Cl ..F16k 19/00 [58] Field of Search ..l37/597, 599, 606, 608, 610, 137/1; 239/444, 548, 558, 562; 425/4, 244,

7/1964 Germany ..239/548 498,774 1/1939 Great Britain ..239/562 Primary Examiner-Robert G. Nilson Attorney-Johnston, Root, OKeeffe, Keil, Thompson & Shurtleff [57] ABSTRACT A distributor for viscous fluid spinning melts or solutions in apparatus for extruding or spinning high molecular weight polymers, especially synthetic fiberor film-forming polymers, the distributor essentially including at least one ring conduit into which there are connected through lateral ports a plurality of sources and sinks for the fluid, there being at least one source with two or more sinks or at least one sink with two or more sources, each source or sink being connected to the ring conduit in an arrangement such that a substantial pressure difference exists as between a source and two adjacent sinks or between a sink and two adjacent sources, and valve means preferably in the form of poppet valves adapted to open and close individual ports while keeping the cross-section of the ring conduit substantially open, thereby maintaining a minimum flow or circulation of the viscous fluid material throughout the distributor.

9 Claims, 8 Drawing Figures PATENTED PRB 1975 3,724,492- SHEET 1 BF 2 INVENTORY FRIEDHELM ITTER ATT'Y'S DISTRIBUTOR FOR VISCOUS FLUID SPINNING MELTS OR SOLUTIONS In the production of filaments, small bands, films or the like in conventional melt spinning or similar extrusion equipment, it is frequently necessary either to distribute a single melt selectively as it is fed from one melt source into different nozzle systems or in other cases to connect different melt sources with a single or multiple nozzle system. This has previously been accomplished by providing reversible valve means between the nozzle system and the source or sources of the melt. In known devices of this type, the polymer melt or fluid had a strong tendency to stagnate and solidify or congeal in the distributor conduit or valve elements after a valve had been turned off to effectively prevent one or more flowing streams of the viscous fluid material. Such a freezing up of individual valves or other distributor portions could be prevented by supplying sufficicnt heat to the valve or the conduit, but with a long retention time at higher temperatures, the stagnant liquid or melt still exhibited typical decomposition phenonema. The disadvantage of known devices thus resides in the fact that the valves and distribution lines either become completely fouled with solid polymer or else the polymer decomposes due to overheating.

One object of the present invention is to provide a special distributor for a highly viscous fluid, particularly spinning melts or solutions of synthetic polymers, whereby'the fluid can be readily distributed from at least one source to at least one sink in the form of a nozzle or other extrusion unit in such a manner that the flow velocity. of the fluid never becomes zero at any point in the distributor system due to the closing off of an individual source or sink. Another object of the invention is to provide a distributor for the viscous polymer fluid wherein dead spaces are substantially eliminated provided that at least one source and one sink remains open out of a plurality of sources and sinks. Yet another object of the invention is to provide a relatively easily constructed distributor which can be adapted for connection with conventional spinning or extrusion apparatus. Other objects and advantages of the invention will become more apparent upon consideration of the following detailed disclosure.

It has now been found, in accordance with the present invention, that one can achieve a substantially improved distributor for a highly viscous fluid such as a polymer melt, in combination with apparatus for spinning or extruding the melt, the distributor maintaining a minimum circulation of the fluid in all portions thereof and including at least one ring conduit to maintain said minimum fluid circulation within a continuous closed circuit, a plurality of fluid sources and sinks, there being at least two of one type and at least one of the other type, connected in fluid communication through lateral ports with the closed circuit of said ring conduit at positions therealong such that a substantial difference in pressure gradient exists as between each of two adjacent positions of the one type and a randomly selected position of the other type, and valve means in said at least one ring conduit to selectively open and shut individual lateral ports, the crosssection of said ring conduit being left at least partly open to fluid flow in both the opened and closed state of said individual ports.

The term source is employed herein to generally designate any means or combination of means to supply a spinning melt or spinning solution to the distributor, and this term may therefore also include the initial extruder and/or pump means which are conventionally used to supply a polymer for spinning or the like. At the same time, the term sink" is employed herein to generally designate the point of consumption or point of use, e.g., the outlets or other lines from the distributor through which the polymer melt or solution is finally delivered to a nozzle, die or other extrusion element. Thus, the term sink" also includes conventional nozzle or die arrangements. in a spinning or extrusion apparatus. As is conventional in fluid dynamics, the so-called sources are of course maintained at a substantially higher pressure than the so-called sinks. In other words, there is a relatively large pressure gradient between every source and any randomly selected sink, this pressure being primarily dependent upon the viscosity of the fluid and the length of the conduit between the source and the sink. In referring to the length of a conduit, it should be further understood that reference is being made to the effective length of the conduit at a particular viscosity and temperature of the fluid polymer material being transported.

The valves employed for purposes of the present invention are most advantageous in the form of so-called poppet valves of a conventional type such that the flanged valve head can be fitted with its relatively flat flow-contacting surfaces fitted against the inner wall surface of the ring conduit or substantially parallel to the flow path of the fluid stream, whether the valve is in the fully opened or in the fully closed state. The valve stems are preferably contained in the distributor so as to be axially projected or moved across the cross-section of the ring conduit without completely'obstructing or closing off this cross-section to the minimum flow of the highly viscous fluid material. V

In referring to a ring conduit, it will be further understood that this term generally refers to a closed circuit pipe line or continuous conduit which need not have a circular or absolute ring shape but may extend in any number of different directions provided that the entire circuit closes upon itself. Depending upon the spinning or extrusion equipment in which the distributor is interconnected, it is of course preferable to maintain the size of the distributor as small as possible, and the height of individual distributor lines or conduits will develop a pressure gradient which is relatively negligible compared to the pressure gradient caused by the high viscosity of the fluid during its frictional flow vide the essential difference in pressure between a source and two adjacent sinks or between a sink and two adjacent sources. In this type of arrangement, it is also desirable to arrange the valves in the ring conduit so as to be displaced laterally asymmetrically from the discharge or entry openings or ports of the additional connecting conduits. In this arrangement as well as in simpler arrangements, there is effectively achieved a different pressure distribution as conditioned by different flow velocities at the mouths or junctions at which the additional connecting conduits are joined with the ring conduit, i.e., such that the pressure drop from one such junction to each of two adjacent sources or sinks is substantially different. This pressure difference, as well as the fact that the valves do not completely block a cross-section of the ring conduit, ensure that a minimum flow of the viscous fluid is maintained even if an individual valve seated in a particular cross-section of the ring conduit is closed. Of course, the flow velocity decreases in comparison to the remaining open portions of the ring conduit, but it is impossible for the melt stream to completely come to rest, and the viscous fluid will not solidify or become decomposed during operation of the distributor with one or even several valves being closed.

In providing different embodiments of the invention, it will be understood that the arrangement of sources and sinks can be of the type in which either a plurality of sources supplies the viscous fluid to a sink arranged centrally, e.g., as in a spinning device, or just the opposite, i.e., where a plurality of sinks as in a nozzle system are supplied by a single centrally arranged source. On the other hand, a viscous fluid or melt can also be distributed from a plurality of sources into a plurality of sinks. In all such arrangements, however, a minimum flow of the viscous fluid through the distributor system is of course guaranteed only if at least one source and one sink remain in operation at all times.

Various embodiments of the invention are more fully illustrated by the accompanying drawing in which:

FIGS. 1 and 2 provide a schematic illustration of one embodiment of a distributor in which two sources are connected to a ring conduit having one sink leading to a single nozzle system or the like;

FIGS. 3 and 4 provide a schematic illustration of another embodiment of a distributor in which a central source is connected by supply conduits to an outer ring conduit containing three sinks leading to conventional spinning nozzles;

FIGS. 5 and'6 provide a schematic illustration of still another embodiment of a distributor having two ring conduits, there being three sources connected to the inner ring conduit and matched with three sinks arranged in an outer ring conduit, the sources and sinks being interconnected asymmetrically by three supply or connecting conduits; and

FIGS. 7 and 8 are similar cross-sectional views of a small enlarged segment of the distributor at a point where the ring conduit contains a lateral port to a source or sink with a poppet valve in either the closed or opened position.

In each of the above noted paired figures of the drawing, the same embodiment is illustrated but with all valves open in one figure while a single valve is closed in the other figure, all as described more fully hereinafter. In addition, it should be noted that the sources and sinks are completely interchangeable in all of the illustrated embodiments, it merely being necessary to reverse the direction of flow in any given case.

. For example, instead of having two sources supplying a single sink as shown in FIG. 1, it is quite easy to visualize that situation in whichtwo sinks are supplied by a single source. This is also true of the remaining figures of the drawing.

The simplest execution of the invention is best illustrated in FIGS. 1 and 2 wherein two sources or supply ports 1 and 2 together with a single sink or outlet port 3 are provided in the ring conduit 4. With all of the valves being open in FIG. 1 and assuming that both sources provide an equal supply of the viscous fluid under the same pressure, one achieves the required difference in the pressure gradient or pressure distribution by providing an interval between the two sources 1 and 2 which is about equal to the interval between the source 2 and the sink 3, the interval between the source 1 and the sink 3 however being equal to double the distance between the source 2 and the sink 3. It should be understood that this is only an exemplary embodiment of the invention, since the spacing or arrangement of the intervals between the sources 1 and 2 on the one hand and the sink 3 with reference to both sources on the other hand is quite optional as long as the interval between the source 2 and the sink 3 in the single ring conduit arrangement shown in FIG. 1 is not equal to the interval between the source 1 and the sink 3. If these intervals between the sink 3 and each of the sources I and 2 are exactly equal or even if they are substantially equal to each other, a flow between the two sources 1 and 2 can no longer take place. In other words, there must be a substantial difference in the pressure drop or pressure gradient as between each of the two different intervals.

The same conditions must be provided with the opposite arrangement in which the two sources 1 and 2 are converted into sinks while the sink 3 is converted into a source. The arrows shown in FIG. 1 must then of course be reversed to show the opposite flow direction after interchanging the sources and sinks.

In FIG. 2, the valve 1 has been closed and is there fore designated by the numeral 1', i.e., the source 1 is completely shut off so that the viscous fluid can flow into the distributor 4 only through the inlet or port 2. As shown by the arrows in the ring conduit of FIG. 2, a minimum flow of the highly viscous fluid is maintained with only the flow between sources 1 and 2 being reversed. This reversal in flow is of course due to the fact that a different pressure relationship exists after closing the valve 1'. If the valve 2 were to be likewise closed, this valve 1 then being opened as in FIG. 1, the flow of the viscous fluid would again be maintained throughout the ring conduit 4. In this simple arrangement, it will also be quite apparent that one cannot completely close the sink 3 or both of the sources 1 and 2 during normal operation of the distributor. However, in this simple device as well as in more complicated distributors, the invention does maintain a minimum flow of the viscous fluid as long as one source and one sink remain open in the entire system. Accordingly, such distributors can be maintained in operation over long periods of time while shutting off individual sources or sinks in such a manner that no section or portion of the ring conduit will result in a dead space, i.e., space in which the flow of the viscous fluid has been reduced to zero.

FIGS. 3 and 4 illustrate another embodiment of the distributor in which a single source is arranged centrally of the device and several sinks,e.g., three separate sinks, are arranged in a single ring conduit. Thus, employing only a single ring conduit 5, a centrally positioned source 6 is connected to the three valved sinks 7, 8 and 9 by means of an equal number of connecting conduits 10, 11 and 12 in order to provide an asymmetric connection at the junction points 13, 14 and 15. Again, one can also visualize the opposite arrangement in which the ring conduit contains three sources while a single sink is arranged in the middle of the distributor. In either case, it will be noted that the asymmetric arrangement of the connecting conduits 10, 11 and 12 essentially providesan inlet or exit opening into the ring conduit 5 at a position which is much closer to one of the valved sinks or sources such as 7 that it is to the other adjacent sink or source 9. In other words, where 6 is a source as shown in FIGS. 3 and 4, any randomly selected sink 7 must be asymmetrically positioned with reference to the source junctions 13 and 14 just as the junction 13 must be asymmetrically placed with reference to the two sinks 7 and 9. Also, since both portions of the fluid stream meeting at each sink must exhibit an equal pressure at the entrance into the sink, the pressure at junction 14 with regard to sink 7 must be greater than the pressure at junction 13. Then, by way of example, if a particular sink is closed such as sink 9 in FIG. 4, the pressure relationships are such that a flow of the viscous fluid is maintained from 15 around to 13 and then into the sink 7 as indicated by the change in the directional arrow for FIG. 4 as compared to FIG. 3.

Still another embodiment of the distributor according to the invention is schematically illustrated in FIGS. 5 and 6. In this instance, several sources 16, 17 and 18 as well as several sinks 19, 20 and 21 are each arranged in their own ring conduits 22 and 23, respectively. These two ring conduits are then interconnected by supply or connecting conduits 24, 25 and 2 6, and in this case, the principle must again be observed that both the sources as well as the sinks are arranged asymmetrically with reference to the closest adjacent junctions 27, 29, 31 or 28, 30, 32. For example, source 16 cannot be positioned symmetrically between junctions 28 and 30 but must lie much closer to one junction 30 than the other junction 28. This is likewise true of sources '17 and 18, as well as each of the sinks 19, 20 and 21. FIG. 6 illustrates the same arrangement as FIG. 5 but with a schematic designation that one sink 21 is closed. Because of the asymmetric arrangement in terms of pressure drop, this closing of the valve for the sink 21 changes the direction of fluid flow between sink 21 and junction 27. In fact, any two sinks can be closed in this embodiment as well as up to not more than two sources, and there will still be a minimum flow of the viscous fluid in the distributor system.

In all of the possible variations in the distributor according to the invention, it is a basic principle that the spacing of the intervals or the flow resistance as a loss of pressurehead between a source and its two adjacent sinks on the one hand or a sink and its two adjacent sources on the other hand, in any optional sequence, must be selected in such a manner that no portion of the distributor conduit is exactly symmetrical or even closely symmetrical with reference to both possible directions of fluid flow. If such symmetry does exist,

then the pressures are exactly counterbalanced and no flow can take place in the distributor between such symmetrical points. Thus, for example, where a source enters into a ring conduit through a lateral port, its flow must be unevenly divided as between two adjacent sinks, and this must be accomplished in such a manner that a different pressure drop or pressure gradient exists between this junction in the point of flow from the source and the two adjacent sinks.

In order to open and close the lateral ports of the individual sources and sinks, it is especially advantageous to employ poppet valves having a relatively conventional construction in order to fit against the inner wall of the ring conduit in either the fully open or the fully closed state of the valve. An exemplary embodiment of such a valve has been illustrated in FIGS. 7 and 8. In these figures, a small enlarged section of the distributor housing or distributor block 33 is adapted to receive an axially slidable poppet valve whose stem or spindle 34 can be moved up or down along the packing 35 held in the block 33 in a conventional manner. The poppet valve essentially consists of the stern 34 having a valve head in the form of a circular flange, the valve seat 36 being formed on the outer edge of the head 37 which is bevelled or conically slanted at about a 60 angle with the valve stem 34. The lower impervious plate or discshaped surface 38 provides the bottom of the valve head while the slanted portion 37 joins with a cylindrical guide member 39 which helps to position the valve in the port. The slanted portion 37 fits intimately and tightly against the correspondingly slanted annular inner surface 40 of the partly hollowed out distributor block 33. Likewise, the bottom surface 38 of the flanged head fits tightly against the correspondingly flat annular surface 41 when the valve is in the open position. As shown in FIGS. 7 and 8, the ring conduit includes a continuous conduit in'a closed circuit with twoi sections thereof 42 and 43 joining with an inlet or outlet port 44 along one side of the distributor block 33.

Thus, the flanged head of the valve is constructed in the conventional manner of a poppet valve so that the bevelled side 37 together with the guide member 39 closes off the inlet or outlet port 44 while the open valve provides a surface member 38 lying on the annular surface 41 so as to protect or relieve the stuffingbox packing 35 while also substantially preventing any dead spaces around the valve head. In the closed position of the valve, this flat surface 38 is exposed to the remaining flow of viscous fluid and is again substantially parallel to the flow of this fluid so as to prevent any dead spaces.

It will be understood, of course, that the individual valve can be provided with even better designs in terms of maintaining the most favorable conditions for streamline flow. For example, the transition between the surface 37 and the guide member 39 can be rounded, for example either convexly or concavely, and still other portions can also be rounded so as to achieve the most favorably streamlined design. For example, it would also be feasible to provide a dome shaped valve head, in the nature of a mushroom-type valve, with a correspondingly spherically shaped surface in order to seat the curved portion of the dome. Also, because of the handling of a highly viscous fluid, it is preferable to provide the valve with a relatively heavy valve stem 34, i.e., so that it has a relatively large diameter of more than 50 percent of the diameter of the flange head. At the same time, however, the valve stem 34 must be sufficiently small to permit an uninterrupted flow of the viscous fluid around this valve stem when the valve is in the closed position as in FIG. 7. In all cases, it will be apparent that the valve must operatively close and open the inlet or outlet port 44 while interfering as little as possible with the flow of viscous fluid through the ring conduit 42,43.

The individual valves can be hand operated in their axial opening and closing movements or else they may be remotely actuated using any conventional control devices. The valves preferably lie completely within the distributor housing or block 33, and the valves can lie in the same plane as the ring conduit 42, 43 or in a separate common plane with the individual segments 42 and 43 of the ring conduit following a non-planar path. The inlets or outlets 44 are easily joined by any suitable connecting flange to a feed or withdrawal line as commonly employed between a source or a sink and a common distributor.'lt is of course desirable to employ relatively short feed lines or withdrawal lines so that they can be readily detached and cleaned after the inlet or outlet has bee closed off by the valve, thereby avoiding any solidification of the molten polymer or any undesirable collection of a viscous polymer solution in these lines. In this respect, the size of the distributor 33 can be varied within a wide range, i.e., so that the distributor can be employed as a very small device as required for a large number of spinning nozzles or spinning plates arranged at close intervals, or else so that a much larger distributor can be introduced between several extrusion sources or the like and one or more extrusion dies or nozzles.

Many variations can then be made in the particular distributor of the invention as employed with conventional spinning or extruding devices, such changes being permissible within the spirit and scope of the present invention. It is essential, however, in all forms of the invention that the pressure drop must be substantially different over the interval between each of two equivalent points of one type, i.e., a source or a sink, and a point of the other type located therebetween in the distribution system. For example, one may select any optional sink in the entire system having a plurality of sinks and sources, and the pressure difference or pressure gradient between this sink and each of the adjacent sources most closely arranged on either side of this sink is very small in one case and very large in the other case. Suitable pressure differences can be readily designed for any given system.

Moreover, it will be understood in the above text that where ever different length's'of a conduit are described or illustrated, this has been done merely for simplification and purposes of illustration, and such lengths must be understood in the sense of pressure drops or resistances to flow, i.e., a measure of the pressure gradient between any two illustrated points. Thus, FIGS. 1-6 of the drawing are highly schematic in this sense, whereas FIGS. 7 and 8 represent one segment of the actual construction. Thus, it must be emphasized that the present invention resides in a particular combination of individual parts and elements rather than in their particular construction other than the preferred use of a poppet valve or similarly constructed valve.

In general, the invention is best adapted for use with a large number of sinks and sources, but the advantages and objects of the invention are also achieved even in a relatively simple arrangement. When employed with a large number of different synthetic thermoplastic polymer melts, especially fiber-forming or film-forming polymer melts, the distributor according to the invention provides excellent service over a long period of operation without freezing up or causing undesirable decomposition of the polymer.

The invention is hereby claimed as follows:

1. In combination with apparatus for spinning or extruding a melt or solution of a high molecular weight polymer in the form of a highly viscous fluid, a distributor which maintains a minimum circulation of said fluid in all portions thereof and which comprises:

at least one ring conduit to maintain said minimum fluid circulation within a continuous closed circuit;

a plurality of fluid sources and sinks, there being at least two of one type and at least one of the other type, connected in fluid communication through lateral ports with the closed circuit of said ring conduit at positions therealong such that a substantial difference in pressure gradient exists as between each of two adjacent positions of the one type and a randomly selected position of the other type; and

valve means in said at least one ring conduit to selectively open and shut individual lateral ports, the cross-section of said ring conduit being left at least partly open to fluid flow in both the opened and closed state of said individual ports.

2. Apparatus as claimed in claim 1 wherein both the sources and sinks are connected to a single ring conduit. I

3. Apparatus as claimed in claim 1 wherein all of the sources are connected to one ring conduit while all of the sinks are connected to another ring conduit, and said ring conduits are joined together in fluid communication by a plurality of connecting conduits.

4. Apparatus as claimed in claim 1 wherein a single source is joined to a ring conduit having a plurality of sinks by means of connecting conduits which are equal in number to the number of sinks and which are arranged in relationship to the sinks such that the pressure drop between an individual sink and each of the two adjacent junctions of connecting conduits with said ring conduit is substantially different.

5. Apparatus as claimed in claim 1 wherein a single sink is joined to a ring conduit having a plurality of sources by means of connecting conduits which are equal in number to the number of sources and which are arranged in relationship to the sources such that the pressure drop between an individual source and eachof the two adjacent junctions of connecting conduits with said ring conduit is substantially different.

6. Apparatus as claimed in claim 1 wherein each lateral port corresponding to an individual source or sink is operatively closed or opened by a poppet valve whose flanged head is seated onto the inner wall of said ring conduit in both the closed and opened state so as to substantially conform the exposed surfaces of the head to the flow of fluid in the ring conduit.

7. Apparatus as claimed in claim 6 wherein the exposed surfaces of the flanged head in at least the closed state of the valve in the lateral port are substantially parallel to the lines of fluid flow in the ring conduit.

8. Apparatus as claimed in claim 1 wherein each source includes means to supply a spinning melt under pressure to said at least one ring conduit.

9. Apparatus as claimed inclaim I wherein each source includes means to supply a spinning solution under pressure to said at least one ring conduit.

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 5,7 9 Dated April .5 973 Inventor (g) Friedhe 1m Itter It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

First page, left-hand column tenth line, insert [30] Foreign Application Priority Data 0 O a I a o P a 6 u Column 7, line 25, "bee" should read been --I Signed and sealed this 27th day of November 1973.

(SEAL) Attest:

* EDWARD M.FLETCHER,JR. RENE, D. TEGTMEYER Attesting Officer I I Acting Commissioner of Patents 

2. Apparatus as claimed in claim 1 wherein both the sources and sinks are connected to a single ring conduit.
 3. Apparatus as claimed in claim 1 wherein all of the sources are connected to one ring conduit while all of the sinks are connected to another ring conduit, and said ring conduits are joined together in fluid communication by a plurality of connecting conduits.
 4. Apparatus as claimed in claim 1 wherein a single source is joined to a ring conduit having a plurality of sinks by means of connecting coNduits which are equal in number to the number of sinks and which are arranged in relationship to the sinks such that the pressure drop between an individual sink and each of the two adjacent junctions of connecting conduits with said ring conduit is substantially different.
 5. Apparatus as claimed in claim 1 wherein a single sink is joined to a ring conduit having a plurality of sources by means of connecting conduits which are equal in number to the number of sources and which are arranged in relationship to the sources such that the pressure drop between an individual source and each of the two adjacent junctions of connecting conduits with said ring conduit is substantially different.
 6. Apparatus as claimed in claim 1 wherein each lateral port corresponding to an individual source or sink is operatively closed or opened by a poppet valve whose flanged head is seated onto the inner wall of said ring conduit in both the closed and opened state so as to substantially conform the exposed surfaces of the head to the flow of fluid in the ring conduit.
 7. Apparatus as claimed in claim 6 wherein the exposed surfaces of the flanged head in at least the closed state of the valve in the lateral port are substantially parallel to the lines of fluid flow in the ring conduit.
 8. Apparatus as claimed in claim 1 wherein each source includes means to supply a spinning melt under pressure to said at least one ring conduit.
 9. Apparatus as claimed in claim 1 wherein each source includes means to supply a spinning solution under pressure to said at least one ring conduit. 